Of course he's not really been hidden all that well. While Waldo books may not be flying off the shelf, he's been making regular appearances in other pop culture icons.
Waldo has made three appearances in The Simpsons through the '90s, including Bart's Comet and Hello Gutter, Hello Fadder.
Homer Simpson: “Waldo, where are you?”
Bizarro cartoonist Dan Piraro's Zen Waldo
In Sibling Rivalry", Stewie and Brian find diversity in an Abercrombie & Fitch catalog with an African-American man dressed like Waldo hidding in an one of the images.
In Imaginationland Episode III, the good imaginary beings fight the evil imaginary creature and Waldo is speared in the chest multiple times.
Of course, there is another explanation of where Waldo has been hiding. He may have lost his memory and now he's out for revenge...
I'll keep my eye out for where else he appears. Many thanks to the Waldo Wiki for all the help.
Previously on Popped Culture...
Suddenly Last Supper
Popaganda: The Pop Culture Revolution
Would You Like Fries With That?
Come as You Are: Nevermind The Parodies